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Introduction      Gears      Gearbox      Electromagnetism
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Figure 4: Electromagnetic induction

In the early 1800s, physicists discovered an important link between electricity and magnetism [1]. They found that when a conducting wire is placed inside a magnetic field that is changing, an electric voltage is induced (generated) in the wire.

This phenomenon, known as electromagnetic induction, is demonstrated in Figure 4. A long wire is wrapped around a cardboard cylinder to form a coil. A voltmeter is connected to the two ends of the coil. When the magnet is moved into and out of the coil (click on the play button), the magnetic field around the coil is changed. The voltmeter's needle fluctuates in response, indicating that a voltage is induced within the coil. The faster the magnet moves, the greater the induced voltage. When the magnet stops moving, the voltmeter's needle instantly returns to zero, showing that a changing magnetic field is required to generate electricity.

Electromagnetic induction is the principle behind the generation of electricity from mechanical energy, be it in small dynamos like the one used by Bigshot or large hydroelectric plants that generate power for our homes.



[1] "Electromagnetic induction." Wikipedia, The Free Encyclopedia. [Online]. Available: http://en.wikipedia.org/wiki/Electromagnetic_induction. [Accessed: Jun 3, 2012].